Preparation And Crystallization Behavior Of CO₂-based Polycarbonate

The fixation and utilization of carbon dioxide (CO2) has aroused widespread concern on worldwide, and CO2as a reactant to complete polymer building has gradually become an important research direction of polymer chemistry, the copolymerization reaction of CO2and epoxy alkane to construct polycarbonate is one of the most promising green reaction, its industrialization has a certain foundation, but it is subject to the physical performance and variety, so the development is slow, mainly because the copolymer are mostly amorphous, and glass transition temperature is low, the strength changes rapidly at high temperature. Based on the problems mentioned above, the work of this paper is mainly about the preparation of high stereo-regularly carbon dioxide based polycarbonates and the study of its crystallization behaviorEpichlorohydrin which is widely used in medicine and resin industry with electron-withdrawing groups is used for the coupling with carbon dioxide to make crystalline CO2-based polymer.’H NMR and13C NMR are carried out for characterization of the molecular structure. The result indicates that the polycarbonates are highly stereo-regular. Differential scanning calorimetry (DSC) is used for the study of thermodynamics. The results of DSC indicate that polycarbonate has a glass translation of38.3℃and a melting point of104.7℃.The enthalpy of fusion is21.02J/g. This result indicates that the crystallization is not completely, amorphous and crystalline structures coexist in polycarbonate. Wide angle X-ray diffraction (WAXD) is carried out for testing the crystal structure. Sharp diffraction peaks were observed at2θ values of14.443°-21.574°and25.1°, demonstrating that the isotactic copolymer is a typical semi-crystalline polymer.Solvent induced crystallization and supercritical fluid are adopted; the effect of dichloromethane, acetone and supercritical carbon dioxide on the crystallization morphology is discussed. DSC result shows the enthalpy of fusion is27.43J/g,17.93J/g and34.13J/g, respectively. The position of sharp diffraction of WAXD testing is the same as the untreated polycarbonate. This phenomenon indicates that solvents and supercritical fluid can induce the crystallization of polycarbonate, supercritical carbon dioxide is the best method.